1. Field of the Invention
The present invention relates to a new structure for monolithic high frequency power amplifiers, with field effect transistors, formed from high speed materials of the family III.V, such for example as GaAs, GaAlAs, InP . . . These integrated amplifiers are matched at the input and at the output and have a high gain and a high output power.
2. Description of the Prior Art
The high frequency amplifier of the invention exists in a plurality of embodiments, with different geometries, which all have the same base, the low or medium power ultra high frequency transistor, having a single input, the gate or the source but having at least two outputs, two drains for example. All the embodiments also have the same structure, in which a plurality of elementary field effect transistors are grouped together in an arborescent organisation. Each elementary field effect transistor may be matched to the same input and output impedance; since it is of low power, it has small geometrical dimension which allows on the one hand a small gate width and on the other hand only a small phase shift between the input and output signals.
Thus each field effect transistor forms the basic module, with one input and at least two outputs, of each stage of the high frequency amplifier. The basic modules are organized in an arborescent structure, that is to say that a transistor of one stage drives at least two transistors of the following stage. All of the outputs of the transistors of the last stage are joined together so as to collect the whole power of the amplifier at a single output. Besides improving the above mentioned electric characteristics, that is to say high operating frequencies and small phase shifts, this structure provides a better input-output insulation, even with a high gain amplifier, and facilitates the geometrical inplantation, which is advantageous for insertion in a more complex integrated circuit, and which permits optimization of the heat dissipation of the amplifier.